Magnetic tweezers
= Magnetic tweezers
A generic instrument for <force> and <torque> uses a magnetically responsive bead in a controlled <magnetic field>, with optical tracking. Translational <force> requires a field gradient. Permanent or anisotropic moments can feel orienting <torque>; an isotropic induced moment parallel to the field has no such <torque>. This definition concerns the physical instrument, without biological applications.